1. Field of the Invention
This invention relates to expansion joints used in structures that are subjected to vehicular traffic, and particularly, to expansion joints used in bridges, roads, parking garages and similar structures.
2. Description of the Prior Art
It is known to have an expansion joint with a flexible seal held between two supports. However, previous expansion joints are either too difficult or expensive to install, maintain or replace; or, the supports do not exert equal pressure onto the seal during expansion; or, the sealing relationship between the seal and the support cannot be maintained for a sufficiently long period of time; or, the seal can tear or rupture due to unequal pressure being exerted on a particular part of the seal; or, the seal cannot be replaced unless the gap in which the expansion joint is located is at or near its widest distance; or, special tools are required to install the seal in the supports; or, that part of the seal located within the supports is unable to participate in the expansion of the joint; or, when the seal is under strain, the seal is not designed to evenly distribute said strain and an area of high strain is created in said seal; or, the seal contains one or more sharp re-entrant corners; or, the seal has insufficient ability to deform transversely; or, the seal is held in the supports by use of an adhesive; or, the supports cannot be readily bent sufficiently in a horizontal or vertical plane without causing the channel to collapse; or, mitreing is necessary when the expansion joint changes in a horizontal or vertical direction.
While expansion joints have been known for some time, it has only been relatively recently that the importance of expansion joints, in extending the usable life of structures in which expansion joints are installed, has been realized. When road salt continuously comes into contact with reinforced concrete supports of a structure, the supports can be severely damaged in a relatively short period of time. By having an expansion joint that has been installed properly and is in poper working order, water containing road salt can be easily drained away from the structure. Seals used in expansion joints are designed to expand laterally by an amount sufficient to cover the expansion of the joint with changes in the temperature.
As long as the seal is properly designed, it will have sufficient expansion capability to cover the maximum width of the joint. However, as the seal ages, it can become brittle and it will then break or crack as the joint expands or contracts. Also, if there are any air pockets in the seal or between the seal and supports, condensation can occur causing a buildup of moisture. If the moisture subsequently freezes, the freezing can cause the seal or the supports to crack or break. A common problem with expansion joints arises when debris, for example, road salt, stones, gravel, dirt, litter or the like accumulate in the joint on an upper surface of the seal. When the level of debris is at or near the level of a road surface where the joint is installed, as wheels of motor vehicles pass over the joint, a significant force is exerted in a downward direction transverse to the seal. If the seal is not designed to distribute this force evenly, the seal can easily be torn or otherwise irreparably damaged by the force exerted on the debris by repeated passage of motor vehicles.
Many expansion joints that are installed extend diagonally across a road surface but are normal to the edge of a sidewalk extending across a structure in which the expansion joints are installed. Thus, many expansion joints have at least two changes of direction. A vertical change of direction up a curve to a sidewalk and a horizontal change of direction between the road surface and the sidewalk. When mitreing is used for either a horizontal or vertical change in direction, the supports must be cut at an angle and various pieces of support must be cut at various angles and then welded together. In some expansion joints, the seal must be mitred as well. In addition to being very time consuming and expensive, mitreing creates a weak point or high area of strain in the expansion joint. If the mitreing is not absolutely perfect, air pockets can be created within the joint. This can cause a buildup of moisture and failure or damage when the moisture changes to ice. Also, as the mitreing is usually done along an edge of the roadway, that is usually the area where most of the water on the structure passes. A leak in that area can be much more serious than a leak in the centre of the structure. In addition, it is very labourious to mitre the supports at a sharp angle, for example, ninety degrees. Normally, previous expansion joints are not mitred at angles of more than forty-five degrees. Also, many previous expansion joints cannot be angled at all or must be angled at angles of equal to or less than forty-five degrees because the seal is too rigid or it will not fit properly in the supports when the supports are angled.